Investigation of Methods to Improve PZT Sol-Gel Deposition Process for Energy Harvesting Applications

Abstract: The purpose of this work was to investigate ways to modify Silex sol-gel deposition of PZT (PbZrxTi(1-x)O3, Lead Zirconate Titanate) in order to improve its properties for energy harvesting applications. A number of methods to improve the figure of merit for energy harvesting (FOM= e312/ε), cause self-polarization, increase lifetime, reduce cost, increase throughput or simplify processing were tested. In order to create a barrier preventing lead diffusion into the substrate, a method to oxidize the bottom electrode’s Ti adhesion layer into TiO2 by RTA (Rapid Thermal Anneal) was tested. Oxidation was successfully achieved and was found to aid in self-polarization, thereby increasing the FOM for films without post-processing polarization. An extended lifetime is expected, but has not yet been confirmed by testing. A seed layer of a different material was tested and compared to a PZT-based seed layer. The new seed layer was found to give highly (100) crystalline PZT with improved self-polarized e31,f and FOM. The new seed layer was also found to be less sensitive to processing variations. Oxygen control during crystallization of the PZT was used in an attempt to generate PZT layers with oxygen vacancies. These hypoxic layers were intended to polarize the film, but were found to reduce the FOM and lead to partial delamination of the film due to stress. A different type of PZT sol-gel was tested as an alternative to the PZT sol-gel in use at Silex. The tested solution was found to result in PZT films with similar properties to those generated by the original type, but the tested type allowed for single layer thicknesses nearly three times thicker than the original type, thereby increasing the throughput and reducing manufacturing costs.